Providing superior electromigration performance and reducing deterioration of sensitive low-k dielectrics in metallization systems of semiconductor devices

Abstract

During the formation of complex metallization systems, a conductive cap layer may be formed on a copper-containing metal region in order to enhance the electromigration behavior without negatively affecting the overall conductivity. At the same time, a thermo chemical treatment may be performed to provide superior surface conditions of the sensitive dielectric material and also to suppress carbon depletion, which may conventionally result in a significant variability of material characteristics of sensitive ULK materials.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]Generally, the present disclosure relates to microstructures, such as advanced integrated circuits, and, more particularly, to metallization systems comprising sophisticated dielectric and conductive materials.[0003]2. Description of the Related Art[0004]In the fabrication of modern microstructures, such as integrated circuits, there is a continuous drive to steadily reduce the feature sizes of microstructure elements, thereby enhancing the functionality of these structures. For instance, in modern integrated circuits, minimum feature sizes, such as the channel length of field effect transistors, have reached the deep sub-micron range, thereby increasing performance of these circuits in terms of speed and / or power consumption and / or diversity of functions. As the size of individual circuit elements is reduced with every new circuit generation, thereby improving, for example, the switching speed of the transistor element...

AI Technical Summary

Benefits of technology

[0015]Generally, the present disclosure relates to process techniques in which a superior performance with respect to electromigration may be obtained, while at the same time the overall electrical performance of the metallization system may be enhanced. For this purpose, the material characteristics of highly sensitive low-k and ULK materials may not be unduly deteriorated, or may even be reestablished, after certain process steps on the basis of a thermo chemical treatment. It has been recognized that, for many sophisticated low-k dielectric materials, the overall behavior of these materials may critically depend on the carbon contents, which may be significantly reduced upon exposure to reactive plasma ambients, as may typically be applied during corresponding cleaning processes and frequently also during the incorporation of a silicon species into exposed surface areas. Consequently, in some illustrative aspects disclosed herein, a thermo chemical treatment may be applied which may result in a significantly reduced degree of carbon depletion upon interaction with sensitive low-k dielectric materials, while a copper-containing metal region may have formed thereon a conductive cap layer which may result in superior electromigration performance and may also act as an efficient mask during the thermo chemical treatment. Consequently, the advantage of a superior electromigration performance without sacrificing overall conductivity may be accomplished by providing the conductive cap layer, while at the same time the thermo chemical treatment may result in superior characteristics of the low-k dielectric material, wherein, in some illustrative embodiments disclosed herein, a further thermo chemical treatment may be performed on the basis of an appropriate process ambient, such as a silicon-containing ambient, which may result in a corresponding improvement of surface characteristics of the dielectric material. For example, a certain degree of etch-related damage of the sensitive low-k dielectric material may be “repaired,” thereby enhancing the surface conditions for the further processing of the semiconductor device, for instance in view of depositing a further dielectric material, such as an etch stop material or any other transition material layer for forming thereon a further low-k dielectric material.

Problems solved by technology

Although silicon nitride is a dielectric material that effectively prevents the diffusion of copper atoms, selecting silicon nitride as an interlayer dielectric material is less than desirable, since silicon nitride exhibits a moderately high permittivity, thereby increasing the parasitic capacitance of neighboring copper lines, which may result in non-tolerable signal propagation delays.

However, for the dimensions of the metal regions in semiconductor devices, the void-free filling of high aspect ratio vias is an extremely complex and challenging task, wherein the characteristics of the finally obtained copper-based interconnect structure significantly depend on process parameters, materials and geometry of the structure of interest.

One failure mechanism which is believed to significantly contribute to a premature device failure is the electromigration-induced material transport, particularly along an inter-face formed between the copper and a dielectric cap layer, which may be provided after filling in the copper material in the trenches and via openings, the side walls of which are coated by the conductive barrier materials.

Moreover, frequently, severe defects may be observed in metallization systems including copper lines with a conductive cap layer formed on the basis of electrochemical deposition techniques, since increased leakage currents and dielectric breakdown events may occur in such devices compared to devices having a metallization system based on a dielectric cap layer.

Although the electromigration behavior of the copper surface may be enhanced in combination with a dielectric cap layer by initiating a silicon / nitrogen diffusion into the surface area of the copper material, it turns out, however, that the degree of inter-diffusion may be difficult to control and also the reactive plasma ambient may result in significant damage of exposed surface areas of sensitive dielectric materials, in particular when ULK materials are used in sophisticated applications.

On the other hand, the copper / silicon compound forming in and beyond the copper surface may have a negative effect on the overall conductivity of the metal line, in particular in metallization systems requiring high current densities, due to the reduced cross-sectional area, which may result in significant signal propagation delays.

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